title: During state 1 to state 2 transition in Arabidopsis thaliana, the photosystem II supercomplex gets phosphorylated but does not disassemble.
abstract: Plants are exposed to continuous changes in light quality and quantity that challenge the performance of the photosynthetic apparatus and have evolved a series of mechanisms to face this challenge. In this work, we have studied state transitions, the process that redistributes the excitation pressure between photosystems I and II (PSI/PSII) by the reversible association of LHCII, the major antenna complex of higher plants, with either one of them upon phosphorylation/dephosphorylation. By combining biochemical analysis and electron microscopy, we have studied the effect of state transitions on the composition and organization of photosystem II in Arabidopsis thaliana. Two LHCII trimers (called trimers M and S) are part of the PSII supercomplex, whereas up to two more are loosely associated with PSII in state 1 in higher plants (called "extra" trimers). Here, we show that the LHCII from the extra pool migrates to PSI in state 2, thus leaving the PSII supercomplex and the semicrystalline PSII arrays intact. In state 2, not only is the mobile LHCII phosphorylated, but also the LHCII in the PSII supercomplexes. This demonstrates that PSII phosphorylation is not sufficient for disconnecting LHCII trimers S and M from PSII and for their migration to PSI.
authors.affiliation: From the Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands.
authors.forename: Emilie
authors.initials: E
authors.lastname: Wientjes
authors.forename: Bartlomiej
authors.initials: B
authors.lastname: Drop
authors.forename: Roman
authors.initials: R
authors.lastname: Kouřil
authors.forename: Egbert J
authors.initials: EJ
authors.lastname: Boekema
authors.forename: Roberta
authors.initials: R
authors.lastname: Croce
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology*; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex
keywords: Photosynthesis; Photosystem II; Plant; Plant Biochemistry; Protein Phosphorylation; State Transitions; Supramolecular Organization